The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, in order to improve the output power of a vehicle engine, it is necessary to increase a displacement, the number of valves, or the diameter of a valve.
However, because the amount of air drawn into an engine is limited through these methods, the output power may not be increased more than a certain level.
Conventional methods use a supercharger or turbocharger to obtain an additional increase in output power.
Particularly, because a turbocharger system, which is widely used in an engine intake system, recycles exhaust energy and thus may increase intake pressure compared to a natural aspirated (NA) system, it has advantages of improving fuel efficiency and increasing power.
Boost pressure means static pressure formed by a turbocharger. As the boost pressure increases, the amount of air intake to a cylinder is increased. Also, with an increase in the fuel amount to be burned, the output power is increased and smoke of exhaust gas may be decreased, thus the increase in the boost pressure is advantageous. However, when the boost pressure excessively increases, the turbine speed increases, and thus durability problems may be caused. Accordingly, it is desirable to control the boost pressure under high-speed driving conditions.
To this end, a Waste Gate Turbocharger (WGT), which decreases boost pressure under high-speed driving conditions and increases the boost pressure under low-speed driving conditions, is used.
Depending on the operation of a Waste Gate Actuator (WGA), exhaust gas may be bypassed to a waste gate, and the boost pressure may be controlled.
When the exhaust gas is bypassed, the energy to the turbine of a turbocharger is decreased, thus the boost pressure effect may be reduced.
Consequently, under low-speed driving conditions, most exhaust gas is used for energy boosting to increase the boost pressure, whereas under high-speed driving conditions, only a part of energy of the exhaust gas is used, thus preventing the boost pressure from excessively increasing.
As related art specifically discloses the description about the WGA.
FIG. 1 is a view showing the connection of a general electronic waste gate actuator, a waste gate valve, and a rod.
As illustrated in FIG. 1, the rod 20 connects the EWGA (Electric Waste Gate Actuator) 10 to the waste gate valve 30 in the document of the related art. The length of the rod 20 is increased due to thermal expansion at hot operation of an engine, but the length is decreased at cold start or cold operation of the engine.
In other words, due to the thermal expansion of the rod 20 and the increase in mileage of a vehicle, the voltage value of the EWGA 10 is changed, thus a warning light of the turbocharger may be lit and poor acceleration in the vehicle may be experienced.